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Category Inosilicate
(repeating unit)
Strunz classification 9.DB.05
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Ccca
Unit cell a = 13.83, b = 20.31,
c = 5.13 [Å]; Z = 8
Color Yellow
Crystal habit Prismatic, acicular to fibrous clusters
Twinning On {100}
Cleavage Perfect on {010}
Tenacity Brittle
Mohs scale hardness 5.5-6
Luster Silky
Diaphaneity Translucent
Specific gravity 2.935-3.031
Optical properties Biaxial (-)
Refractive index nα = 1.610 nβ = 1.628
nγ = 1.630
Birefringence δ = 0.020
Pleochroism Distinct; X = Y = pale yellow;
Z = colorless
References [1][2][3]

Carpholite is a manganese silicate mineral with formula Mn2+Al2Si2O6(OH)4. It occurs as yellow clusters of slender prisms or needles. It crystallizes in the orthorhombic system.

The carpholite group includes ferrocarpholite, magnesiocarpholite, vanadiocarpholite, and potassiccarpholite.

Discovery and occurrence[edit]

It was first described in 1817 for an occurrence in Horní Slavkov (Schlaggenwald), Karlovy Vary Region, Bohemia. The name derives from Greek karfos for "straw" and lithos for "stone" due to its crystal habit.[3]

Its typical occurrence is in shales that have undergone low grade metamorphism. Associated minerals include sudoite, manganoan garnet, chloritoid and fluorite.[1]